Concentrated flaming arc lamp for projectors



P. R. BASSETT. CONCENTRATED FLAMING ARC LAMP FOR PROJECTORS. APPLICATION FILED JUNE26, 1920.

l ,42 8, 51 O. Patented Sept. 5, 1922.

1 J mm llg INVENTOR FREE 7'L7N AYE/15% HIS ATTORN Y.

b State of New York, have invented certain Patented Sept. 5, 1922.

UNITED STATES PATENT OFFICE.

PRESTON B. BASSE'IT, OI BROOKLYN, N. Ya, ASSIGNOR TO THE SPERBY GYBOSCOPE.

COMPANY, OF BROOKLYN, N. Y., A CORPORATION OF NEW YORK.

commw'ma'ran rmumo sac LAMP ron rnomc'roas.

Application filed June 26, 1920. Serial No. 391,973.

J'o all whom it may concern.

Be it known that I, Pnns'roN R. Bassm'r, a citizen of the United States of America, residing at 1716 Newkirk Avenue, Brooklyn, New York, in the county of Kings and new and useful Improvements in Concentrated Flaming Arc Lamps for Projectors, of which the following is as'pecification.

This invention relates to methods of securing by means of flaming arc electrodes a concentrated, brilliant light very similar to what is known as the high intensity arc, which consistsin emanations located in the crater of a flaming are operated at high cur rent density and rapid electrode consumption, said arc being operated by direct current, in which instance the' prlncipal light source is in the positive crater.

Heretofore black body radiation running from 150 to 200 candle'power per square millimeter, usually nearer the former, has been from a number of scientists, 'and especially by. the introduction of the mineralized car-e bon, or by compound electrodes with a mineralized core and carbon shell, so that recently it has been possible to produce an electric arc of very much greater brilliancy emanatin from the location of the positive crater. o accomplish this, however, it has been thought necessary, and so stated in'the patent art, that very much higher current densities were required than had heretofore been used. Also very rapid consumption of the positive carbon was employed, resultin both from the high current density employe and the fact that the thin positive electrodes employed were provided with a relatively lar e highly impregnated core, while the shell of more refractory, pure carbon was not more than twice the core diameter. For

. instance, in the Sperry high intensity searchlight employing 150 amperes the positive electrode is only about 5" in diameter, as compared to 11" diameter for a pure carbon arc ofthe same current, while the core of said Sperry electrode is about In other words, the core has full 332;% of the area of the shell, while the big intensity electrode as a whole has only about one-third of the cross sectional area of the pure carbon elec- -considered to be the trode. Similarly 'with the high intensity light in my prior Patent 1,328,311, Method of o crating flaming arc lights for projectors, January 21, 1920, a small' positive electrode is employedhavin a core fully half the diameter of the shel The rate of consumption of each is approximately nine inches an hour. It will readily be seen that such a rate of consumption is so rapid as to lessen the commercial advantages of the "emp oying approximately the same current ally ushered in by work upon this subject and at the same time to greatly increase both the total candlepower and concentration of the source without increasing, and in fact decreasing, the watts consumed. y invention has'special reference to the production of a concentrated, intense light source for the rojectionof motion pictures in which rapid burning electrodes are so serious a light, such as for motion picture projection drawback as to render the, high intensity light as now made impracticable.

By my invention I not only increase the total light emanated but greatly increase the light thrown on the screen beyond the increase in total light by concentratin the light source substantially entirely within the crater of the positive electrode, in. other words by reducing the light source more nearly to an ideal point at the focus of the projector. ,At the same timesI greatly decrease the rate of electrode consumption over present forms of high intensity lights and the total watts consumed.v In brief, to accomplish my invention I at .once increase the overall size of the positive electrode and decrease the size of the highl impregnated core as employed in the high intensity light, within certain well defined limits, however. Referring to the drawings in which is now preferred form of my invention is shown:

Fig. 1 shows a preferred burning condition in which the positive electrode has a core of substantially the correct-size and the carbons are positioned at the preferred angle.

Fig. 2 shows an alternative burning condition which, while notnow considered as satisfactory as the burning condition shown in Fig. 1, will produce superior results to the present type of are employed in motion picture projection Fig. 3 shows a poor burning condition arising from the employment of a positive electrode with too small a core.

Fig. 4 shows the same are as the flames a pear during a portion ofthe burning of t e arc, the appearance of the flames alternating between the position shown in Fig. 3 and the position shown in Fig. 4.

Fig. 5 is a view showing the manner in which the present type of positive electrode used for high intensity flaming arcs and designed to employ approximately double the current of that shown in Fig. 1 would burn if an attempt were made to operate it under the conditions of Fig. 1. i i

As before stated, the.rate of consumption of electrodes in the high intensity lamp is very rapid and while the light produced is equal to, or it may be superior in total candlepower to the'light produced by my in- "ventionand'the concentration'of the source excellent, the rate of electrode consumption is such as tobe commercially impracticable. Not only does the rapid rate of consumption increase the cost by requiring close attention on the part ofthe operator and frequent extinguishing for replacing the electrodes but the character of the long, slender, large cored electrodes used in high intensity lamps renders them individually expensive. T hese.

. same amperage. In fact, the electrode I employ is very'nearly the same size as a pure carbonelectrode of thesame amperage and does not vary materially from present standard practice. For a current of 70 amperes,

- which has been foundto' give good results under the working conditions of this invention, anelectrode of about fi" is preferably. employed, as compared to for 75 am- .pere high intensity lamps as illustrated 'in my sai'd prior patent. The increase in cross section area is, therefore, more than a hundred per cent. The diameter,it will be seen, is substantial] the same as the diameter of pure carbon e ectrodes'now used according to the best practice in projector work for this current. As low a current as from 45 to 50 amperes has also been found to give cerium, etc.). Also in sharp contrast to'the standard high intensity flaming arc electrades the core is very small as compared to the shell, the diameter ratio being 1 :4 or 5 and the area of the core bein only about w th to 15th the area of the s ell as compared to a standard core-shell area ratio for high intensity arcs of 1:4. The electrode, therefore, is not operated at as high a current density as the high intensity are which usually exceeds 400 amperes per square inch of area of the positive electrode, but is operated at moderate current density, i. e., from 200 to 300 amperes per square inch of area of the positive electrode, it being very probable, however, that the very small, highly impregnated core carries a heavy current. The mineralization of the core is preferably high. Fifty per cent mineralization has been found to give good results. The reason for the very low carbon consumption will be at once apparent, since by both the increase in the overall size of the electrode and the decrease in the size of the rapidly consumed core, the area of the slow burning shell is increased almost three fold and the area of the core decreased to less than one-half.

The negative electrode 4 is preferably provided with a core 5 having a different density froriLthe shell 6, being preferably much harder than the shell. Both core and shell however, may be of pure carbon, or at least not impregnated with flaming arc materials. The negative electrode is preferably smaller than the positive being about onehalf the diameter of the positive. When a hard core is used it tends to protrude slightly beyond the normal rounded surface of the negative electrode as-shown at 7. The size and characteristics of the electrodes are given byway of example, only for a current of'froni 65 to 75 amperes. It will be understood, of course, that with an increase or decrease in current (within limits) the size of each electrode should vary in proportion.

The preferred position for the electrodes is with the positive facing the projecting lenses indicated at 8 and 9 and, therefore,

substantially horizontal, with the negative at a steep angle thereto (say 55), as shown in Fig. 1. When in such position the negative flame 13 rises substantially vertically past the positive crater 14 touching the same only at the crater face without enveloping it. The arc length employed is also unusually short, i. e., about 3; or less. The short arc length, coupled with the low re sistance of the flaming are, results in. a verv low voltage drop across the are, i. e. about i to volts as compared to a pure carbon horizontal arc of the same amperage of to volts. Ver marked spindling of the positive electrode takes place at 1'5 owing to the fact that it is slowly consumed. Since,

however. the shell is very thick it does not spindle down to the core, as described in my.

previous Patent 1,328,311, but forms a fairly deep crater 14 somewhat as indicated in Fig. 1. In said crater is confined the globule 10 of glowing white hot vapors forming the concentrated, principle light source, of the are which compares favorably vith the high intensity arc. The strength of the current employed, however, is not suflicient to cause the ball of light to project, at leastmarkedly, beyond the crater but remains within the crater. With the carbons in this position the positive electrode is preferably rotated to maintain the crater symmetrical substantial, oblique crater 10 is formed which has the advantage of being faced in the general direction of the lenses. The

- crater is, as a rule, deep enoughto maintain carbon may be adjusted laterally, princi-' the high intensity vapors within the same. Such lamps are usually designed so that each pally so that the negative can be advanced beyond the alinement with the positive to maintain the obliquity of the crater. It is found that the operator, by advancing and retracting the negative electrode, can maintain a fairoblique crater.

The reduction of the size of the core can, of course, be carried to too great an extent, however. This extreme is illustrated in Figs. 3 and 4 and results in two different burning conditions which alternate, the are passing from one to the other as the rapidly burning core 3' first burns back to such a great depth (Fig. 3) that the flame 13 leaves the core 3 and jumps to the shell 2. When this occurs the arc reverts to the'ordinary are and loses not only over half its total candlepower but also its light concentration. When the shell has burned back to the core the flaming materials from the core again enter the flame at 10, as shownv in Fig. 4, producing a fairly good are until the condition shown in Fig. 3 again arises. Such an arc is, of course, unsatisfactory for motion picture pro'ection. v In order to avoid the burning con itions arising asshown in Figs. 3 and 4 the diameter of the core should not be reduced below about one-sixth of the diameter of the shell. 1

0n the other hand, if too large-a core is employed, the concentrated, intense light source will disappear altogether. Fig. 5 shows a high intensity electrodedrawn to the same scale as Fig. 1 and designed for operation at 'over double the current, i. e. 150 amperes; The diameter of the electrode 20 is the same as my electrode using amperes, while the core 21' is as compared to 3;" in my electrode. The figure illustrates such an electrode operated at 70 amperes, i. e., the same current and current density as employed in Fig. 1. No high intensity effect or concentrated light source isobtained, however, the are appearing as an ordinary white flamin are.

Having described my invention, what I claim and desire to secure by Letters Patent is: 1

1. The method of producing a concentrated flaming are without the employment of high current density and rapid electrode consumption, which consists in employing a positive carbon having a small, highly mineralized core of as high diameter ratio to the shell as 1:4 and a negative electrode of less diameter than the positive and operating such are at ordinary current density.

2. The method of producing a concentrated flaming arc of moderate current and electrode consumption, which consists in employing a positive carbon having a small core impregnated with flaming materials and a pure carbon shell of at least four times the diameter of said core, said carbon being of not materially different diameter from the standard non-flaming electrodes for the same current in conjunction with a non-flaming negative electrode of less diameter, and,

operating such are at less voltage drop than such standard non-flaming are at the same current.

3. The method of producing a concentratameter from the standard non-flaming electrodes for the same current in conjunction with a non-flaming negative electrode having a hard core, and operating such are at less voltage drop than such standard nonflaming are at the same current.

4. The method of producing a. concentrated flaming are without the'employmen't of high current density and rapid electrode consumption, which consists in employing a positive carbon having a small, highlyminrent density and at short arc length.

5.. The method of producing a concentrated flaming are without the employment of high current density and rapid electrode consumption, which consists in employing a positive carbon substantially twice the diameter of the positive carbon of the standard high intensity are for the same current and having a small, highly mineraized core of as hih diameter ratio to the shell as 1:4 an

and operating such are at ordinary current density and low voltage drop.

6. The method of, producing a concentrated flaming are without the employment of high current density and rapid electrode consumption, which consists in employing a positive carbon having a small, highly mineralized core of as high diameter ratio to the shell as 1 :4 and a negative electrode and relatively positioning said electrodes during the burning of the arc for an arc length of not substantially more than one-quarter of an inch and at such an angle that the negative flame sweeps vertically past the positive crater without enveloping the tip.

-7. The method of producing a concentrated flaming arc. of moderate current and electrode consumption, which consists in employing a. positive carbon having a small I a negative elec-., trode of less diameter than the positive core impregnated with flaming materials and a pure carbon shell of at least four times and not more than six times the diameter of said core, said carbon being of .not materially different diameter from the standard non-flaming electrodes for the same current in conjunction with a non flaming negative electrode of less diameter, and operating such are at less voltage drop than such standard non-flaming arc at the same current.

8. The method of producing a concentrated flaming are without the employment of high current density and rapid electrode consumption, which consists in employing a positive carbon substantially twice the diameter of the positive carbon of the standard high intensity are for the same current and having a small, highly mineralized core of as high diameter ratio to the shell as 1 :4 and posltionin the negative electrode at a steep angle an not more than 1}" from the positive electrode.

9. The method of producing a concen-,

' PRESTON R. BASSETT. 

